Protein C inhibitor regulates both cathepsin L activity and cell-mediated tumor cell migration.

BACKGROUND: Protein C inhibitor (PCI) is a plasma serine protease inhibitor (serpin) that regulates several serine proteases in coagulation including thrombin and activated protein C. However, the physiological role of PCI remains under investigation. The cysteine protease, cathepsin L, has a role in many physiological processes including cardiovascular diseases, blood vessel remodeling, and cancer. METHODS AND RESULTS: We found that PCI inhibits cathepsin L with an inhibition rate (k(2)) of 3.0x10(5)M(-)(1)s(-)(1). Whereas, the PCI P1 mutant (R354A) inhibits cathepsin L at rates similar to wild-type PCI, mutating the P2 residue results in a slight decrease in the rate of inhibition. We then assessed the effect of PCI and cathepsin L on the migration of human breast cancer (MDA-MB-231) cells. Cathepsin L was expressed in both the cell lysates and conditioned media of MDA-MB-231 cells. Wound-induced and transwell migration of MDA-MB-231 cells was inhibited by exogenously administered wtPCI and PCI P1 but not PCI P14 mutant. In addition, migration of MDA-MB-231 cells expressing wtPCI was significantly decreased compared to non-expressing MDA-MB-231 cells or MDA-MB-231 cells expressing the PCI P14 mutant. Downregulation of cathepsin L by either a specific cathepsin L inhibitor or siRNA technology also resulted in a decrease in the migration of MDA-MB-231 cells. CONCLUSIONS: Overall, our data show that PCI regulates tumor cell migration partly by inhibiting cathepsin L. GENERAL SIGNIFICANCE: Consequently, inhibiting cathepsin L by serpins like PCI may be a new pathway of regulating hemostasis, cardiovascular and metastatic diseases.

Video-assisted thoracic surgery for primary spontaneous pneumothorax in children: is there an optimal technique?

OBJECTIVE: Video-assisted thoracic surgery (VATS) for treatment of spontaneous pneumothorax refractory to nonoperative management was first reported in children by Rodgers in 1986 (Ann Surg. 1986; 204:677-680). Small series have shown success with apical blebectomy, mechanical or chemical (talc) pleurodesis, or combination techniques. We report the largest pediatric series of VATS for primary spontaneous pneumothorax (PSP) to date, to assess outcomes and compare techniques. METHODS: Retrospective review of all children undergoing VATS for PSP between 1999 and 2007 at 2 university-affiliated hospitals by the same group of surgeons. Mann-Whitney U tests and chi(2) used (P < .05 = significant). RESULTS: Thirty-two patients underwent 41 VATS procedures (32 initial-30 unilateral, 2 bilateral; 9 subsequent-7 contralateral, 2 ipsilateral recurrences). Mean age at presentation was 16.5 years (range, 13-20 years). Blebs were identified at the time of VATS in 95% of patients, but in 12.5%, they were on lower lobes. Mean duration of postoperative air leak was 2.7 days, postoperative hospital length of stay was 5.0 days, and postoperative chest tube duration was 5.1 days; 2 patients required Heimlich valves, which were managed at home. Five different surgical techniques were used as follows: blebectomy plus mechanical pleurodesis had the shortest length of stay (4.3 days) and need for chest tube drainage (4.1 days) but had a higher recurrence risk (6% major, 16% minor) than blebectomy plus chemical pleurodesis. The risk of requiring an additional VATS procedure (ipsilateral or contralateral) was 28%. Mean follow-up was 46 months. CONCLUSIONS: Blebectomy plus either mechanical or chemical pleurodesis were both associated with acceptable outcomes. Blebectomy plus chemical pleurodesis appears to have less risk of ipsilateral recurrence but longer postoperative stay and chest tube drainage.